1. Field of the Invention
This invention relates to a method of providing electrical power at an underwater installation, a method for providing auxiliary electrical power to an underwater well installation, the installation being linked to a surface location via an umbilical cable, to supplement any electrical power received at the installation from the umbilical cable, an underwater well installation and a facility including such an installation.
2. Description of the Prior Art
Underwater installations, for example subsea hydrocarbon extraction wells and well fields having a number of such wells, are typically supplied with electric power from a surface or land-based source via insulated copper cores within an umbilical cable. Typically, such umbilicals also carry hydraulic power lines, enabling certain control functionality at the well, and chemical flow lines for servicing the well.
As an umbilical ages, the insulation around the copper cores may degrade, for example through water ingress or chemical degradation. The cores themselves may also degrade. Such degradation may result in a reduction in the capacity of the cores to transmit electricity so that the well is unable to function adequately. Currently, the only solution to this problem is to replace the umbilical, which is very expensive.
Additionally, it is often the case that fields developed in the past reach the end of the infrastructure's design life, but may still be capable of producing hydrocarbons. Operators may therefore need to upgrade the infrastructure to extend the field life. The upgraded infrastructure usually has a higher power consumption than the original development, for example due to the need for more sensors for monitoring ageing equipment, increased electronics generally and more measurements of produced fluid due to changes etc.
The original umbilical will have been designed to cater for the original power requirements, and so may be inadequate for the upgraded equipment. The operators are then faced with the choice of either replacing the umbilical, which as noted above is very costly, or limiting the amount of equipment placed subsea, which is commercially undesirable.
Systems having forms of underwater power generation are known from US 2006/0006656, US 2005/0179263, WO2009/122174, GB 1595529, U.S. Pat. No. 4,112,687, WO 97/23708, US 2006/016606, XP002532127 (OTC 15366, 5 May 2003, pp 1-8), U.S. Pat. Nos. 4,781,029 and 3,568,140.
It is an aim of this invention to address the problems described above. In particular, the invention provides a much cheaper alternative to the drastic solution of replacing the umbilical, and allows upgrading without limitations. This aim is achieved by providing auxiliary power generation means at the installation, to supplement the power received at the installation from the umbilical. In a particular embodiment, the auxiliary power generation means comprises a chemical flow battery.
Using the invention, either or both of the voltage and current carried by the umbilical cable can be increased to meet demands of well tree equipment.